EyeWorld India September 2016 Issue

September 2016 EWAP CORNEA 65 cases. Here he uses a concentration of 0.02% for 12 seconds following the laser treatment and prior to bandage lens placement. “I also use mitomycin at the same concentration when removing Salzmann’s nodules after a superficial keratectomy with application for 30 seconds via a sponge soaked in MMC,” he said. MMC pearls When removing the MMC, Dr. Lee recommends using two bottles of balanced salt solution after the time allotted for washing this off the ocular surface. “If using for pterygium surgery, it should never be applied to bare sclera,” he said. He advised practitioners to be cautious that the concentration is not too great or applied for too long. “The big things that I see as a cornea specialist are overuse of MMC or using too high of a concentration, which does cause stem cell deficiency,” he said. “That’s one thing that we see with glaucoma patients because [the physician] has used it for 2 minutes, sometimes 3 minutes, and there can be superior stem cell deficiency from using it.” Dr. Lee also stressed the importance of ensuring that the concentration is accurate as this is usually specially prepared. “I’ve seen physicians make concentration errors,” he said, adding that this is where it can be helpful to have an experienced compounding pharmacy mix it. “We’re lucky enough to have a compounding pharmacy right in our surgery center, so when we’re doing PRKs or lamellar keratectomies, it’s nice to go next door, and they make it up for us and give it to us that morning.” While the drug Mitosol (Mobius Therapeutics, St. Louis) is commercially available at traditional pharmacies, Dr. Lee finds that this can at times be difficult to obtain. “The problem is that it gets back-ordered a lot, so in my experience it’s been hard to get that dependably.” To avoid complications, Dr. Rapuano stressed the importance of keeping MMC away from the limbus and the conjunctiva, when used in conjunction with excimer laser surgery. “It’s applied just on the cornea,” he said. “You don’t want there to be too much of the mitomycin liquid on the sponge because it will drip off and go where you don’t want it to.” Ideally, the physician wants the sponge to be moist, but not super wet. “I suck it up off the sponge right before I’m going to remove it from the eye,” Dr. Rapuano said, adding that he uses a dry Weck- Cel sponge to remove any excess that might otherwise spill onto the conjunctiva. He then irrigates the area with two bottles of saline. As long as physicians keep the MMC on the cornea following excimer laser surgery without spilling into other areas, there should be very little chance of a patient ending up with limbal stem cell deficiency, Dr. Rapuano noted. This is something to be particularly wary of with pterygium surgery. “Pterygium may be a limbal stem cell abnormality to begin with,” he said, adding that this is why the vessels grow onto the cornea. To avoid complications stemming from MMC, Dr. Rapuano recommended keeping this away from the limbus, either just under the conjunctiva or just on the cornea away from the limbus. For pterygium surgery with MMC, he stressed the importance of always having conjunctiva covering the bare sclera. “If you’re using mitomycin, I think that you have to have some sort of tissue, such as conjunctiva or amniotic membrane, to cover the bare sclera because there have been numerous reports of scleral melts,” he said. This is especially true when the sclera is not covered with either conjunctiva or amniotic membrane. In addition to MMC applied by the practitioner, Dr. Lee noted that topical MMC drops can be used for patients with ocular surface squamous neoplasia. However, this is not usually his first choice. “I prefer using topical interferon alpha at 1 million parts per unit QID for several months,” Dr. Lee said. “But if patients cannot afford the medicine, I will place lower punctal plugs and use topical mitomycin 0.02% QID for 1 week with 1 week off and then a second week of treatment at the same dose.” The interferon alpha is easier on the eye, but can cost up to $1,000, whereas the MMC usually ranges from $75 to $200, he said. Use of MMC is contraindicated for those with corneal edema or those with severe dry eye, autoimmune dry eye, and compromised corneal endothelium. In such patients, the MMC is too toxic for the surface of the cornea. “With dry eye patients, it can damage the stem cells,” Dr. Lee said, adding that it can make dry eye worse and can cause corneal and scleral melts. For corneal edema patients, it is toxic to the corneal endothelium. Overall, Dr. Lee urged caution when using MMC in pterygium surgery. However, with other types of procedures, he said the chances for complications are much lower. “Long-term effects on the corneal endothelium are not known, but short-term corneal complications are minimal when using short application times and vigorous washing of the ocular surface after PRK or keratectomy cases,” he concluded. EWAP References 1. Lindquist TP, et al. Mitomycin C-associated scleral stromalysis after pterygium surgery. Cornea . 2015;34:398–401. Editors’ note: Drs. Lee and Rapuano have financial interests with Bio-Tissue (Doral, Florida). Contact information Lee: lee0003@aol.com Rapuano : cjrapuano@willseye.org procedure. Their results, which will be published soon, include observations that the regeneration of the limbal stem cells is permanent. “Why [SLET] is an important breakthrough is that it makes limbal stem cell therapy accessible to patients and surgeons alike,” Dr. Basu said. “[There are] trained corneal surgeons who are working all over the world with patients who needed treatment but were not able to provide it to them either because they did not have a stem cell laboratory or because they didn’t want to do a radical therapy like conjunctival limbal grafting. What SLET does is it bridges this gap. “We want more people with LSCD to get treatment that will help them see,” Dr. Basu said. He thinks SLET is the procedure that will accomplish that. EWAP References 1. Sangwan VS, et al. Simple limbal epithelial transplantation (SLET): a novel surgical technique for the treatment of unilateral limbal stem cell deficiency. Br J Ophthalmol . 2012;96:931–4. 2. Basu S, et al. Simple limbal epithelial transplantation: long-term clinical out- comes in 125 cases of unilateral chronic ocular surface burns. Ophthalmology . 2016;123:1000–10. 3. Vazirani J, et al. Autologous simple limbal epithelial transplantation for unilateral limbal stem cell deficiency: multicentre results. Br J Ophthalmol . 27 January 2016. [Epub ahead of print] Editors’ note: The physicians have no financial interests related to their comments. Contact information Amescua: gamescua@med.miami.edu Basu: sayanbasu@lvpei.org Positive outlook - from page 61